1. Field of the Invention
The present invention relates to a process for recording by jetting liquid droplets through a spout (orifice) with thermal energy and to a recording liquid effectively applicable to said process, in particular to a recording liquid excellent in thermal stability.
2. Description of the Prior Art
Non-impact recording processes have become of interest in recent years in that they generate noises in a negligible degree during recording operation. Among these processes, a very powerful method is the so-called ink jet recording process (the liquid jet recording process), which is capable of high-speed recording, in addition, onto plain paper, requiring no special treatment like so-called fixing. Accordingly, until now a variety of techniques for this process and devices for realizing them have been proposed, some of them having been commercialized by adding improvements and some others being under developments to which many efforts are now continuously exerted for commercialization.
Of these techniques, for example, the liquid jet recording processes disclosed in Japanese Patent Kokai No. 51837/1979 and German Patent Offen (DOLS) No. 2843064 are distinguished from other liquid jet recording processes in the characteristic of excerting thermal energy to a liquid as energy for producing liquid droplets, thereby gaining driving force for jetting of liquid droplets.
That is to say, in these recording processes, the liquid subjected to the action of thermal energy undergoes a state change accompanied by an abrupt increase in its volume, and the liquid droplets are jetted from an orifice in a recording head with the force caused by said state change, and fly and adhere to recording paper or the like, thus recording being accomplished.
In particular, the liquid jet recording process of DOLS No. 2843064 has advantages in that it can not only be effectively applied to the so-called drop-on demand recording, but readily realize a high-density multi-orifice recording head of full line type, thereby achieving high-speed recording of image of high resolution and high quality.
While having such various advantages, said liquid jet recording process needs to be improved in the life span in repeated use, i.e., the durability, of recording head for the purpose of recording a high resolution and high quality image over long hours at a high speed or in order to extend the service life of recording heat outstandingly.
Factors determining the service life of the recording head applied to such a recording process include, besides the life of an electric energy-thermal energy transforming element employed, the deposition of solids onto the surface of said transforming element. That is, in the liquid jet recording process of the above-mentioned patent, the recording liquid, if thermally unstable, is liable to undergo chemical change because it is exposed to a high temperature during repetition of the generation and extinction of bubbles by heating, with the result that insoluble matter forms and deposits on the wall of the heating zone of the recording head, which, in turn, renders the recording head to be eventually incapable of discharging the liquid therethrough. Accordingly, the thermal stability of recording liquid is very important for continuing high-speed recording for long hours by use of such apparatus.